Vibratory machinery such as screens, conveyors, shakeouts, and the like conventionally include a trough-like material support which is oscillated in an orbital path to advance material along the length of the support. The orbital oscillation of the support conventionally is effected by at least one motor driven shaft journaled for rotation on a base and having one or more eccentric sections drivingly coupled to the material support. In the assembly of an eccentric shaft of conventional construction with the vibratory machinery, the shaft is supported on the base by outboard bearings and the eccentric portion or portions of the shaft are accommodated in inboard bearings which are coupled to the material support. To faciliate assembly oversize inboard bearing openings have been provided which have had to be fitted with specially shaped (crescent) bushing inserts to conform such bearing openings to the configuration of the associated portions of the shaft. While carrying no greater load than the outboard bearings, the inboard bearings have had to be larger and consequently less economical to use.
The utilization of bushing inserts has also not been altogether satisfactory for a number of reasons. For example, considerable time is involved and the use of bushing inserts does not always result in precision alignment of the eccentric shaft with the several bearings, as a consequence of which operation of the machinery may be adversely affected and excessive wear of the relatively movable parts may result, thereby accelerating the necessity of replacement of such parts.